Donald Trump’s new ad on terrorism and immigration provides an occasion to step back and make a larger point about his entire candidacy that continues to get a bit lost in the daily back-and-forth.

It’s this: Trump presents himself as a great fixer. But his zeal to present himself as a master manager has led him to offer simplistic solutions that not only dumb down the very complex problems we face; they would actually work against efforts to solve them.

Trump’s ad claims that “in Hillary Clinton’s America, the system stays rigged against ordinary Americans,” and by way of illustration, goes on to claim that “illegal immigrants convicted of committing crimes get to stay.”

That simple juxtaposition captures Trump’s whole candidacy in a nutshell.

Trump’s fundamental argument is that illegal immigrants — particularly those of the most criminal variety — continue to get over on ordinary Americans, with the help of complicit leaders who rig the system in a way that allows that to continue. Since Clinton would continue the policies of our current leadership, she would maintain the rigged status quo.

Trump’s designation of “illegal immigrants convicted of committing crimes” is inadvertently revealing of the fallacy at the core of his whole vision. In one sense, of course, all illegal immigrants have broken the law. But Trump singles out those who have committed crimes on top of that, in order to make the system’s current failures seem particularly menacing and in need of maximal Trumpian solutions.

But, generally speaking, Trump’s solutions would make rooting out the most criminal illegal immigrants harder, not easier.

The basic question at the core of our immigration debate is this: What should we use our deportation resources for, given that those resources only allow for the deportation of a fraction of the undocumented population?

Sitting at the very core of Trump’s vision is the goal of mass deportations — i.e., the proactive removal of all 11 million undocumented immigrants. It’s the policy goal that originally launched his candidacy and rocketed him to the top of the GOP primary pack. It’s a goal his core supporters continue to support. It’s the idea that has given his candidacy — and Trumpism as a movement — much of its energy: All illegal immigrants must be removed, and only Trump is strong and “politically incorrect” enough to carry it out.

By contrast, Obama, Clinton, and most Democrats want to prioritize the removal of only the most criminal and dangerous of the undocumented. To do this, they advocate for legalization of the vast bulk of undocumented immigrants — those with jobs and longtime ties to communities who don’t pose a threat. In their vision, this would allow limited enforcement resources to be focused only on the removal of the most criminal and dangerous undocumented immigrants.

As Simon Rosenberg has argued, this basic difference has animated the immigration argument between the two parties for years. Republicans have steadfastly opposed the Obama administration’s efforts to prioritize the removal of the most serious criminals, so the administration has continued to look for executive ways to focus resources on that population, via revisions of enforcement priorities and so forth (this led to the legal standoff over his executive actions). As Rosenberg notes, this focusing of resources has already succeeded in making the border more manageable, too, despite Trump’s continued depiction of it (in the new ad and elsewhere) as overrun by dark hordes.

But in Trump, this core underlying difference has been pushed forward in a way that has unmasked the Republican position as unsustainable. Most Republicans have long known that mass deportations would be too costly and cruel and disruptive to be even remotely realistic. So they essentially continued to argue for keeping undocumented immigrants in the shadows — keeping them subject to removal — while not quite advocating mass deportations.

Trump, by contrast, has made his whole campaign about proactive mass removals. And that has forced a recognition of the key underlying point: Mass deportations are never going to happen. The resources will never be appropriated for it, and indeed, the public (and many Republican lawmakers) would, in the end, not stand for it.

Once this is fully understood, Trump’s posture on this issue — the central one of his campaign — collapses in on itself. Trump wants to “unrig” the system to remove the most criminal undocumented immigrants removed more quickly. But he also insists that our resources should be used to deport everyone, which makes prioritizing the former more difficult. The fantasies Trump is peddling — ironically enough, in the course of offering himself as a master manager who can easily fix everything — make the actually achievable goals harder to realize.